Contents available on the Internet have gone through an explosive transformation in recent years. The static texts or still picture images in the web pages that impressed early online users have been replaced by dynamic animations, rich multimedia video clips, and dynamic web page layouts. In addition, contents in web pages have become interactive at runtime; the users can use input devices (e.g., mouse or stylus) or user's fingers to move or rearrange objects within web pages for rich customization.
One of the driving forces in this interactive development is the use of script-content in the form of computer-executable instructions that can be executed by the applications or software (e.g., a web browser) at or near runtime. One example of such developments is a mashup or mash-up, which is a web application that combines code and behaviors from various sources for integration within an experience or for creating new experiences. However, due to the nature of the browser, as mash-ups are executed when it is rendered or before it is rendered, most mash-ups are creating implied trust relationships between the host site and third-party code within the web pages. This trust-relationship puts web-sites and the underlying web business models at risk. In addition, because of the interactive nature of mash-up codes or scripts, the trust-relationship may also put the user's personal or private content presented on the web pages and/or local device at risk.